2011 5.3 dropping to zero load while driving

I am currently wracking my brain trying to figure this one out for a customer. The truck has had a cam swap, other than that it is completely stock.

He calls me several days after the initial tune and said he was experiencing a jerk while driving the truck so I went to see what the issue was. Upon driving the truck that I not just a jerk but a commanding thud that will bounce your head off the dash for a split second while driving and it will resume operation as normal.

I immediately looked for transmission issues, monitored it closely and upon close examination I noticed that this 2011 six speed truck magically has a tune for an A4 in it??? 🤷*♂️ He then tells me that the dealership replaced the trans over a year ago. It is most assuredly a 6. I overwrote everything with a matching stock 2011 engine and trans tune and started from scratch. Same issue.

MAP stays constant, engine load drops to zero, the timing and fuel follow suit, 50* and lean AF for a split second obviously being where the giant jerk is coming from. This is not an issue that the motor will live through long and I am at a complete loss.

Does he have HP Tuners as well? Or some other means of programming the TCM?
I'm certain that it didn't change on it's own.

If you have the original calibration file, just to a Write Entire to the TCM.

If it has AFM, try turning it off.